| 1 | # Selector Specificity
|
|---|
| 2 |
|
|---|
| 3 | [<img alt="npm version" src="https://img.shields.io/npm/v/@csstools/selector-specificity.svg" height="20">][npm-url]
|
|---|
| 4 | [<img alt="Build Status" src="https://github.com/csstools/postcss-plugins/workflows/test/badge.svg" height="20">][cli-url]
|
|---|
| 5 | [<img alt="Discord" src="https://shields.io/badge/Discord-5865F2?logo=discord&logoColor=white">][discord]
|
|---|
| 6 |
|
|---|
| 7 | ## Usage
|
|---|
| 8 |
|
|---|
| 9 | Add [Selector Specificity] to your project:
|
|---|
| 10 |
|
|---|
| 11 | ```bash
|
|---|
| 12 | npm install postcss @csstools/selector-specificity --save-dev
|
|---|
| 13 | ```
|
|---|
| 14 |
|
|---|
| 15 | ```js
|
|---|
| 16 | import parser from 'postcss-selector-parser';
|
|---|
| 17 | import { selectorSpecificity } from '@csstools/selector-specificity';
|
|---|
| 18 |
|
|---|
| 19 | const selectorAST = parser().astSync('#foo:has(> .foo)');
|
|---|
| 20 | const specificity = selectorSpecificity(selectorAST);
|
|---|
| 21 |
|
|---|
| 22 | console.log(specificity.a); // 1
|
|---|
| 23 | console.log(specificity.b); // 1
|
|---|
| 24 | console.log(specificity.c); // 0
|
|---|
| 25 | ```
|
|---|
| 26 |
|
|---|
| 27 | _`selectorSpecificity` takes a single selector, not a list of selectors (not : `a, b, c`).
|
|---|
| 28 | To compare or otherwise manipulate lists of selectors you need to call `selectorSpecificity` on each part._
|
|---|
| 29 |
|
|---|
| 30 | ### Comparing
|
|---|
| 31 |
|
|---|
| 32 | The package exports a utility function to compare two specificities.
|
|---|
| 33 |
|
|---|
| 34 | ```js
|
|---|
| 35 | import { selectorSpecificity, compare } from '@csstools/selector-specificity';
|
|---|
| 36 |
|
|---|
| 37 | const s1 = selectorSpecificity(ast1);
|
|---|
| 38 | const s2 = selectorSpecificity(ast2);
|
|---|
| 39 | compare(s1, s2); // -1 | 0 | 1
|
|---|
| 40 | ```
|
|---|
| 41 |
|
|---|
| 42 | - if `s1 < s2` then `compare(s1, s2)` returns a negative number (`< 0`)
|
|---|
| 43 | - if `s1 > s2` then `compare(s1, s2)` returns a positive number (`> 0`)
|
|---|
| 44 | - if `s1 === s2` then `compare(s1, s2)` returns zero (`=== 0`)
|
|---|
| 45 |
|
|---|
| 46 | ## Prior Art
|
|---|
| 47 |
|
|---|
| 48 | - [keeganstreet/specificity](https://github.com/keeganstreet/specificity)
|
|---|
| 49 | - [bramus/specificity](https://github.com/bramus/specificity)
|
|---|
| 50 |
|
|---|
| 51 | For CSSTools we always use `postcss-selector-parser` and want to calculate specificity from this AST.
|
|---|
| 52 |
|
|---|
| 53 | [cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test
|
|---|
| 54 | [discord]: https://discord.gg/bUadyRwkJS
|
|---|
| 55 | [npm-url]: https://www.npmjs.com/package/@csstools/selector-specificity
|
|---|
| 56 |
|
|---|
| 57 | [Selector Specificity]: https://github.com/csstools/postcss-plugins/tree/main/packages/selector-specificity
|
|---|
